1. Field of the Invention
Apparatuses and manufacturing methods consistent with the present invention relate to an optical lens, and more particularly, to a variable focus optical lens that provides miniaturization and thin size, and reduces the cost and improves productivity by simplifying the structure and manufacturing process.
2. Description of the Related Art
In general, an optical lens is a transparent body or lens having at least two refractive curves. The optical lens is widely used in various applications, such as cameras, telescopes, and microscopes.
For example, a camera module using an optical lens is used for a personal mobile terminal, such as a cellular phone or a personal digital assistant (PDA), as well as a camera set. Recently, the personal mobile terminal has been developed as a multipurpose electronic device having various multimedia functions, such as a camera, a game, a music player, broadcasting, and connecting with the Internet, in addition to a simple audio transceiver function. Also, attempts to integrate more functions in a small area have been made for the personal mobile terminal.
Furthermore, the camera module has recently developed auto focusing, auto zooming, and an auto macro function to obtain better images. However, when a camera module for a personal mobile terminal is manufactured to have these various advanced functions, the camera module is limited in its size, due to the size of a lens and a mechanical lens driving gear.
In other words, to obtain the advanced functions, unlike a basic lens, a lens for each type is required, such as a proximity lens, a standard lens, a telephoto lens, and a zoom lens, and the lens should be exchanged with another lens, depending on the intended use. To achieve auto focusing, the focal distance of the lens should be varied. Since a separate motor or driver is required to control such variations, a problem occurs in that the whole size of the camera module increases.
To solve such a problem, a liquid lens (or fluid lens) based on electrowetting has been suggested. The liquid lens achieves auto focusing and auto zooming by using its curvature variation. According to the electrowetting technology, a voltage is externally applied to an electrode coated with an insulator and a conductive fluid to eliminate surface tension of the conductive fluid when the conductive fluid and a nonconductive fluid are in contact with each other on the electrode, whereby a contact angle of the conductive fluid and a shape of a boundary between the two fluids are varied. The liquid lens based on electrowetting has an advantage in that a small sized camera module can be obtained as no mechanical lens motion is needed.
However, the related art liquid lens has several problems. As the liquid lens is manufactured for each chip by separate process steps, the number of manufacturing process steps increase, thus the manufacturing cost increases and productivity is reduced. Also, a problem occurs in that a high driving voltage is required to create the flow of fluid and to apply a hydraulic pressure to the fluid. Furthermore, a problem occurs in that the response time required for focusing increases.
Moreover, when the hydraulic pressure (or flow) is applied to the fluid, a problem occurs in that it is difficult to dispense the exact amount of the fluid. In particular, local strain unstably occurs in a boundary portion between a lens portion and a channel and thus the exact amount of the fluid is not dispensed. This deteriorates reliability and stability.